[FLINK-12122] Spread out tasks evenly across all available registered TaskManagers - ASF JIRA

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Details

Type: Sub-task
Status: Closed
Priority: Major
Resolution: Fixed
Affects Version/s: 1.6.4, 1.7.2, 1.8.0
Fix Version/s: 1.9.2, 1.10.0
Component/s: Runtime / Coordination
Labels:
- pull-request-available

Release Note:
In order to use a scheduling strategy which is more similar to the pre FLIP-6 behaviour where Flink tries to spread out the workload across all available `TaskExecutors`, one needs to set `cluster.evenly-spread-out-slots: true` in the `flink-conf.yaml`

Description

With Flip-6, we changed the default behaviour how slots are assigned to TaskManagers. Instead of evenly spreading it out over all registered TaskManagers, we randomly pick slots from TaskManagers with a tendency to first fill up a TM before using another one. This is a regression wrt the pre Flip-6 code.

I suggest to change the behaviour so that we try to evenly distribute slots across all available TaskManagers by considering how many of their slots are already allocated.